英语：This is what happened to the famous mammoth which was found preserved and in good condition /这就是在那个著名的猛犸象身上发生的是,他被完好的保存可起来 书上说which was found 是定语从句这个明白,但是后面又说preserved and in good condition 是主语补足语 怎么就是主语补足语了呢?求语法帝!